text:
In the US, in the last 50 years, have there been any accidents known to involve a student pilot intentionally practicing stalls in solo flight?
In the US, in the last 50 years, have there been any accidents known to involve a student pilot intentionally practicing stalls in solo flight?
This question is asked in the context of civilian flight training in single-engine land airplanes.
I've heard of at least one flight school prohibiting student pilots from practicing stalls solo.

I'm not sure how a flight school could effectively bar a student from doing something solo?  There's no flight recorder on most student planes.   So long as you don't do it directly over the FBO, how would they ever know?

You realise that statistics won't change your flight schools procedures, right? You use their planes, you're subject to their rules. Buy your own plane, you can do what you like! With the caveat that until you have your license you're flying on someone else's. And if they dont approve you for the flight, you're not licensed.

@abelenky there's the NTSB (or AAIB) test. Always ask yourself: would you want what you're about to do to be documented in an accident report. "Student pilot with 35 hours was practising stall recover while flying solo in preparation for their skills test when they entered a spin and was unable to recover before.....".

@Jaimiec I understand that all pilots flying a rented plane are expected to follow whatever rules the owner may care to impose, and also that all student pilots must follow whatever conditions their instructor imposes, which may in turn be partly an expression of the policy of the flight of the flight school.  The question is not about looking for loopholes but rather more about best practices.  But, the actual stated question is just about statistics, or rather, about any occurrences of accidents.

And for that reason, its a perfectly fine question. Just dont expect it to change anyone's mind.

Yes.
I did a search of the NTSB database, limiting my search to final reports with a search term of "practicing stalls." This lead to about 50 reports. I scanned the reports where the aircraft was a typical trainer, such as a Cessna 172 or Piper Cherokee. I found three reports this way that involved a solo student pilot practicing stalls. Interestingly, only one of these seems to be due to a failure to recover from the stall.
12/2/1990 A student pilot experiences engine roughness and eventual failure during stall practice. Cause: failure to apply carb heat during low power settings, leading to carb ice.
3/22/1989 A student pilot fails to recover from a stall, while practicing too low to the ground. A factor involved was the featureless, snow covered terrain that made it difficult to gauge altitude above the surface.
11/5/1982 A student pilot experiences engine failure due to a stuck valve during stall practice.

difficult to gauge altitude above the surface oh wow..... I tend to use that little dial-y thing with the scale down one side and the numbers on it.

That only tells you altitude above the sea-level.  Especially in rough terrain, it is worthless for telling you altitude above the surface, (unless carefully coordinated with accurate reading of a Sectional)

@abelenky ...unless you're right next to the airport and the altimeter is set for QFE.

@aCVn Unlike in Europe, in the US we never set the altimeter to QFE. Below 18,000' it is always MSL.

I guess I'm really most interested in whether there are any cases where the student spun in and crashed, or mushed down through thousands of feet of altitude and crashed,  while practicing stalls at what would seem to be a prudent altitude.  Or oversped/ overstressed the aircraft during recovery.  And so on and so forth.  But, that's not what the question states.  Examples so far seem to be engine-related or involving stall practice at too-low of an altitude.


text:
Do most flight schools and FBOs in the US prohibit student pilots from practicing stalls while flying solo?
Do most flight schools and FBOs in the US prohibit student pilots from practicing stalls while flying solo?
This question is asked in the context of civilian flight training in single-engine land airplanes.
I've heard of this policy actually being in effect with at least one flight school.
"Most" means more than half. "Student pilot" is not meant to include anyone who holds a pilot's license for airplanes or for that matter for gliders.
The reference to FBOs means that they are renting an aircraft to the student pilot involved.
The question is asking about a blanket prohibition that would include a student who is close to being ready to take his or her checkride, not something only applied to (for example) the first few solo flights.
People who have had personal experience with a large number of flight schools and FBOs will be in the best position to answer this question.

This really is a different question than the one that was originally on hold.  My intention was to roll back the on -hold question to its original form and then delete it.  Not sure the roll-back worked but since I deleted it it should vanish soon anyway.

This answer to another question is an example of one specific flight school with severe restrictions on what maneuvers a student pilot could perform solo-- https://aviation.stackexchange.com/questions/52994/are-there-any-training-maneuvers-that-are-only-allowed-when-flying-with-a-flight/53040#53040

What exactly qualifies something as a "flight school"?  It could be anything from Embry-Riddle down to a CFI giving you instruction in your own plane...

Well, I guess I could change the question to something like "Is it the norm for a student pilot who is almost ready to take his checkride to be prohibited from practicing stalls while flying solo, either by his instructor or by the aircraft owner or by a clause in an insurance policy?"  -- would that be better?  "Norm" specified to mean in this case more than half the time.

But there's still the problem of gathering statistics from all those diverse places that do flight instruction.  All I can say is that it was not the case when I did my PPL at a smallish FBO, but that was several decades ago.

The two flight schools I have used had this rule and all of the other local places I know of also have this rule. The FAA no longer recommends full break stalls during training anyway you merely need to bring it to the horn. Interestingly enough the data does not support the decision

Student pilots are, by far, the least likely to suffer stall/spin
  accidents, as a proportion of in the pilot population. Pilots holding
  FAA Airline Transport Pilot (ATP) certificates are also less likely to
  stall/spin.

Although a case can likely be made that limits like this are what make student pilots least likely to stall/spin.

"The FAA no longer recommends"... shocking.

@quietflyer the change came right after my check ride and I was quite surprised as well. They did not do a great job pushing the info out as many instructors I speak to dont seem to know about the change.

@Dave - It keeps changing. Your link is from 2017. The 2018 Private ACS requires a recovery after a full stall.  2018 Commercial: At the first indication OR after a full stall, as specified by the examiner.  The new 2019 ATP: At the first indication

I did my PPL training in a flight of Tomahawks in 2006. We would routinely fly stalls until after the break in solo training. I never spun one, either!

This is nuts.  In Canada spins are still taught.  No wonder the airlines have a problem with new pilots who don't really know how to fly airplanes.

Training and experience cannot be replaced.  Stalls should be practiced to hone recovery skills and to AVOID spinning the aircraft.  Do them with an instructor at safe altitudes.  Recent lift graph published by Tanner Swett revealed the horrors of allowing a spin to be established:  above a certain AOA lift RISES to a second maxima at 45 with much higher drag (on the inside wing). This seems to be a major contributer to a spin "going flat".  Learning to control and correct in incipient stages is key to avoid this.  An untrained person is far more likely to make a critical control input error.

My CFI was fine with me practicing stalls while soloing for my private.  I know that doesn't provide a general answer, but this question can really only be answered by survey anyway.

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text:
Does pumping fuel to each wingtip affect roll trim in a stabilized turn?
If an aircraft is stabilized in a constant-bank, constant rate turn with no sideslip, and then we pump 200 gallons of fuel from a fuselage tank to a tank on the tip of each wing, without changing the position of the ailerons or rudder, and without changing the aircraft CG, will we find that the aircraft tends to roll into the turn, roll out of the turn, or neither?
The intent of this question is that we get the aircraft fully stabilized in a coordinated turn at the original bank angle after pumping the fuel to the tips, and then we put the controls back in their original positions and see if the aircraft tends to roll.  This isn't meant to be a question about the effects of suddenly redistributing the mass and the way that this might possibly create a temporary yawing tendency due to yaw rotational inertia, like we see when a skater throws out their arms horizontally while spinning around.

This question is related to effects discussed in this answer, and in recent accompanying comments -- https://aviation.stackexchange.com/questions/12515/could-a-plane-be-constructed-to-be-fly-in-fixed-stick-roll-stable-circles/12526#12526

If the CG doesn't change and the controls don't change, why would the aircraft do something different?

See the link in first comment-- there's a claim there (with a diagram) that lots of weight in the wings causes an inertial (centrifugal) rolling-out tendency.  My intuition is that this is not correct but I am not certain yet.

Not sure whether this is related or not-- https://aviation.stackexchange.com/questions/65628/what-is-the-formula-for-the-bank-angle-required-for-a-turn-in-line-abreast-forma

Not if the fuel pumped to the wing tips in equal amounts so that the lateral CG is unchanged.  But... there are effects related to the inertia of the fuel mass (the wings become spokes in a flywheel, you could say).
I have some flying time a plane that has all of its fuel in the wing tips, in tuna fish shaped tanks, 25 usg per side.
The difference in handling qualities with the tips nearly full and the tips nearly empty is all related to inertial effects of the fuel mass; roll rate, roll inertia, yaw inertia, and roll response to yaw.  The roll rate you can generate by skidding the plane is much lower with the tips full.  The influence of dihedral in damping and restoring roll deviations is reduced.  Disturbances are amplified because of the flywheel effect of the tip mass and this is especially noticeable in yaw; there is more of a tendency for the tail to wag in bumps.
But in a stabilized bank in smooth air, the amount of fuel in the tips made no difference in increasing or decreasing overbanking/underbanking, except to the extent that the interia of the fuel dampens or inhibits the usual restorative forces.  So if you had an airplane that can be banked and holds the bank angle with no input, there is no major effect of fuel in the tips in changing that characteristic, until you hit a bump and the inertial effects start to work.  However, where the airplane has an overbanking or underbanking tendency, the flywheel effect will inhibit it starting and tend to keep it going once started.
So to answer the basic question, if you had a plane that naturally wants to roll out of a turn when inputs are removed, the effect of fuel in the tips will be to reduce that effect somewhat, so it will still roll level but take longer, and once level it will tend to overshoot more.  It it wants to overbank into a spiral dive, same thing that way.

That all makes sense.  The ultimate point of the question is to shed light on (for or against) the theory that lots of mass in the wings tends to create an inertial roll torque towards wings-level, as suggested in the related answer linked in the first comment.

Overall I would say from experience that mass in the wing tips is a net negative and would much prefer the fuel mass as inboard as possible.

Everything in your answer makes sense to me, but I might ask if you ever specifically tried a careful test to see if changing the distribution of mass (more towards the tips versus more towards the fuselage) affected roll trim.  It seems like it would be hard to do such a test if you were just slowly burning down fuel, all of which was in the wingtip tanks.  Btw what plane was this?  Would be nice to know-- that's pretty unusual for ALL the fuel to be in tip tanks.

It was a homebuilt called a PL-2 http://pazmany.com/wp/?cat=15.   It was very sensitive to differential fuel volume.  The fuel quantity became your roll trim.  When solo you needed about 2 gal more in the right side than the left to counter the pilot's offset weight in the cockpit.  All I can say is I never noticed more or less inherent stability with the tips full vs nearly empty, only the various inertia effects.

Here is how I see the problem at this time--
There's no doubt that in a turn, there's a rolling-in torque (toward a steeper bank angle) created by the difference in airspeed, and lift, between the inboard and outboard wingtips.
Does concentrating the mass at the wingtips reduce this roll torque?  Obviously roll inertia is increased, but is the roll torque actually reduced?
Let's say we attach a string to the CG and sling the airplane around and around in a circle, somewhat in the matter of a "control-line" model airplane, but with the wings at the zero-lift angle-of-attack, so the aerodynamic roll torque noted in the first paragraph disappears.  Is there any intrinsic, inertial tendency for the aircraft to roll to a wings-level attitude, rather than adopting a steeply-banked attitude?  A tendency that, if it existed, might be more pronounced if the wingtips were heavily weighted?  It intuitively appears to me that the answer is "no".
Therefore the answer to the original question intuitively appears to be "no".
One could argue that the outboard wingtip, travelling at a larger velocity and experiencing more apparent "centrifugal force" than the inboard wingtip, will tend to dominate the situation and therefore there WILL be some very small self-leveling effect, and more so if the weight is concentrated near the tips. This effect appears to have some similarity to a "tidal" effect in orbital dynamics-- it would be based upon the different radii experienced by different parts of the body in the orbit or turn.  This effect is surely a very minor player in roll stability dynamics in a normal turn-- unlike in a flat spin, where the center of rotation may be near the center of the aircraft, and any weight added to the wingtips will strongly tend to make the spin go even flatter.
This may be a situation where it is actually most helpful to adopt a reference frame based on the moving aircraft itself.  This will not be a valid inertial reference frame, so we'll have to take "centrifugal force" into account.  In a fully coordinated turn, the direction of the apparent weight of each tip tank will be straight down in the aircraft's reference frame, but the outboard tip tank will seem to "weigh" more than the inboard one, and this create a rolling-out tendency, or to put it another way, will cancel out the rolling-in tendency created by the difference in airspeed between the two wingtips.  A perfectly span-loaded aircraft will experience no rolling-in or rolling-out tendency due either to the difference in apparent weight, or the difference in lift, at different points along the wingspan. If all the weight is concentrated at the wingtips, this would appear to create some self-leveling effect.

Ultimately it will take some equations to shed some light on the significance of any such self-levelling tendency due to inertial effects--

Effects of moving fuel would be transitory, eventually restabilized by trim, provided CG did not change significantly.
Pumping fuel out to the tips would naturally slow the roll rate momentarily, but since roll acceleration is governed by roll drag, over time roll rate would resume unchanged (In a stabilized turn, roll is constant, the roll out of the turn would be slower with the same control input).
More interesting is the effect on yaw.  Fuel in the fuselage moves at speed x around a circle.
Inside wing speed is x-y and outside wing is x+y.  So effect of moving fuel to the slower inside will speed it up a bit, and the faster inside wing will slow it down a bit. The result is a yaw to the outside, that again, aerodynamic force will overcome.
As ultimately all aerodynamic motion is governed by drag, effects of moving weight laterally on an equal basis are only temporary, if control inputs are not changed.

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text:
How may one notify the FAA of the apparent flaw in the airspace design at KEGE?
Several questions and answers have addressed the design of the airspace around KEGE.  The situation is perhaps best summarized in this answer -- Can the Class-E-to-surface airspace near Eagle County Regional airport KEGE be ignored when the tower is open? .  How may one notify the FAA of this apparent flaw in the design of the airspace?  Note that this is not a charting error, but rather an apparent error or omission in the way the airspace has been designated, as described in the "Airspace Designations and Reporting Points" document JO 7400.11C.

From the JO 7400.11C, page (ii)

Request for Information.  For further information, contact the Airspace Policy Group, Federal Aviation Administration, 800
  Independence Avenue, SW, Washington, DC  20591; telephone: (202)
  267-8783.

They will likely connect you with the specific airspace coordinator for the region of interest.


text:
In the US, is it legal to cover up some of the required gyro instruments during flight under IFR in actual IMC?
In the US, is it legal to cover up some of the required gyro instruments during flight under IFR in actual IMC?
The purpose being for "partial panel" practice.

What makes you think it's illegal @quietflyer?

So the answer is yes, it is legal to cover up some of the gyro instruments during flight under IFR in actual IMC?

@GdD intuitively, there may be restrictions on this; as your own answer notes, it's a spectacularly bad idea. It's a reasonable question.

To my knowledge there's nothing illegal about practicing partial panel in real IMC, however it's a spectacularly bad idea to do so. A failure of vacuum instruments in IMC is an emergency because you can easily lose orientation and dig a big hole in the ground. A safety pilot won't be able to help unless they have a separate set of instruments to rely on, and even then upset recovery in IMC is inherently less safe.
If you want to practice partial panel pleeeeease do so in VMC, with a safety pilot.

Well, obvious bad ideas are illegal by the catch all “careless and reckless” rule.

I have to admit I'm projecting a cockpit where pilot and copilot have two different gyro displays. In this particular case, you need only cover one side.

Well, the regulation uses the phrasing "careless or reckless", so clearly careless operation is prohibited, and reckless operation is prohibited, and operation which is both careless and reckless is prohibited. Although that would be a pretty hilarious loophole: "What I'm doing is both careless AND reckless, so it's permitted!" (The entire paragraph says: Aircraft operations for the purpose of air navigation. No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.)

14 CFR 91.205(a) states (emphasis added):

(a) General. Except as provided in paragraphs (c)(3) and (e) of this section, no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation described in paragraphs (b) through (f) of this section unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition.

So the question is: if an instrument is covered, then is it "in operable condition"?
My interpretation would be no: if an instrument is covered, then you can't see what it says, so it's not in operable condition. That would mean that, if that instrument is required for flight, then flying with it covered is illegal.
That said, someone might disagree and say that the instrument is in operable condition, because you can simply remove the cover in order to see what it says. I would disagree with that, because a covered instrument clearly does not provide the safety benefits that an uncovered instrument does.
I did a search in the FAA's "Letter of Interpretation" database, and there didn't seem to be any letters about whether or not a covered-up instrument is "in operable condition". So it seems like this question hasn't been legally decided yet.

I think it would be very much prudent to not fly partial panel in IMC. The line of thought on inoperability of instruments however, when taking it to the extreme, surely means that if an instrument becomes inoperable if you hold something in front of it, unfolding a sectional chart in IMC is a no-go, too... (and you could probably make that point, but it would not be very practical).

Obviously one concern is that an instrument is covered, no one is monitoring it for potential failure-- but this is more an issue of prudence than legality-- thanks for the well-considered answer

@CptReynolds Yeah, that's an interesting point. There's undoubtedly a continuum of "operable" to "inoperable". If an instrument is hidden behind an object for just a brief moment, but you can (and you're intending to) see it again almost immediately, then that's clearly "operable". If an instrument is hidden by a cover that's glued on, so that it would take you several minutes of effort in order to see it, then that's clearly "inoperable". So "operability" must depend on how much effort is required in order to view the instrument.

91.205 deals with IFR, not IMC. If the post-it note on an instrument renders it "inoperative" for 91.205 purposes then doing that in VMC on an IFR flightplan is prohibited too.  Do you think that is the meaning here?

@RalphJ Yeah, the requirements in 91.205 are based on VFR or IFR flight, not the weather conditions. So that would seem to mean that if you want to practice partial panel flying (and you don't have another pilot on board with full instruments), then you must do it under VFR.

@TannerSwett  Is that the generally understood rule in the community of flight instructors & DE's and feds?

@RalphJ No idea; I've never even flown in IMC. All I know is the actual text of the regulation.

Regarding "operable condition": if an MFD is operating normally & the instructor turns its brightness to full dim, essentially blanking the display, is it no longer in an "operable condition"? What if he turns it off? Is there no difference between "operable condition" and "operating"?  Is a landing light only "operable" when it is turned on & illuminated?

Let us continue this discussion in chat.


text:
May the Class-E-to-surface airspace near Eagle County Regional airport (KEGE) and Marshall AAF (KFRI) be ignored when the tower is open?
May the Class-E-to-surface designation indicated by the dashed magenta lines outside the dashed blue circle at Eagle County Regional airport (KEGE) be ignored when the tower is open?
Likewise at Marshall AAF (KFRI)?
Normally we would consider a dashed magenta line that does not actually enclose the airport whose approaches it protects to denote a Class-E-to-surface "extension", i.e. E4 airspace.  The "extension" would be described in the E4 section of the "Airspace Designations And Reporting Points" document (FAA Order 7400.11C), typically with no comment about effective hours.  Meanwhile, if the tower is not open 24 hours, the area in the dashed blue circle will be typically described in the Class D section of Order 7400.11C and ALSO in the E2 section of 7400.11C, with a note in each section to see the A/FD for the effective hours of that designation.
Here is an example of an airport with airspace designated in this manner: KMFR.  The relevant pages in JO 7400.11C are E-80, E-189, and D-65.  The dimensions of the E-2 airspace are identical to the dimensions of Class D airspace, except for the absence of any altitude ceiling on the Class D.  The E-4 "extensions" are in effect 24/7, whether the tower is open or closed.
But at KEGE and KFRI that's not what was done.  There is no listing for the airspace within the dashed magenta line in the E4 section of JO_7400.11C.
Instead, a single area of Class-E-to-surface "Surface Area designated for an airport", i.e. E2 airspace, is defined that includes the area in the dashed blue circle AND the area in the dashed magenta line that abuts the dashed blue circle.  (Page E-70 KEGE, page E-16 KFRI).
There's a note that the dates and times that the E2 will be in effect will be published in the A/FD: for example, for KEGE we read "This Class E airspace area is effective during the specific dates and times established in advance by a Notice to Airmen. The effective date and time will thereafter be continuously published in the Airport/Facility Directory.
AMENDMENTS 11/23/06 71 FR 46077 (Revised)"
Naturally, the airspace in the dashed blue circle is also described in the Class D section of Order 7400.11C (page D-59 KEGE, page D6 KFRI), with a note to see the A/FD for the effective times.
The A/FD (for KEGE) says "AIRSPACE: CLASS D svc 1400–0200Z‡; other times CLASS E."
No E4 airspace has been designated for KEGE or KFRI.
So the area in the dashed blue circle is Class D when the tower is open and E2 when the tower is closed.  And the area enclosed by the dashed magenta line, has, oddly, been designated not as E4 airspace as per normal practice, but rather as part of the same E2 airspace that is only in effect when the tower is closed.  So it seems that the entire E2 airspace should vanish when the tower is open, and should therefore simply become Class G up to 700' AGL.
Surely this is not what is actually intended.
Is the intention that the area inside dashed magenta border but outside the dashed blue circle stays E2 the whole time, while the area inside the dashed blue circle and below 9100' MSL at KEGE or below 3600' MSL at KFRI falls out of the E2 as if it were cut with a cookie cutter, and turns into Class D, when the tower is open?
Here's one problem with that idea--
There are about twenty other airports in the US where the airspace designation is similar to KEGE and KFRI, but a little different.  One such example is KUNV-- University Park at State College PA--  --for the others, see this related answer: What are all the US airports where E4 "extensions" change to E2 and become part of a larger E2 "surface area" when the tower closes for the night?.
Taking KUNV as an example, the airspace enclosed by the dashed magenta lines is designated in order 7400.11C (page E-171) as E4 airspace, with a note to see the A/FD for the effective hours.    There's ALSO a designation of E2 airspace (page E-37) that includes the exact same airspace AS WELL AS the area in the dashed blue circle, with a note to see the A/FD for the effective hours.  And the area in the dashed blue circle is also described in the Class D section of Order 7400.11C (page D-23), with a note to see the A/FD for the effective hours.
The note in the A/FD simply says "AIRSPACE: CLASS D svc 1100–0300Z‡; other times CLASS E."
Clearly, in this case it was felt that the entire E2 airspace would vanish as a single unit when the Class D airspace was in effect, hence the need to also have an E4 airspace designation to protect the airspace in the dashed magenta projections when the tower is open.
The same situation applies at the other 20 airports listed in the linked answer.
Added note-- it is interesting to note that on the FAA's LAANC map for authorization for sUAS (drone, model airplane) flight the projecting "extensions" at KEGE and KFRI are NOT covered by the grid squares that indicate the areas where pre-authorization is required. All other E2 airspace IS covered by the grid square that indicate that pre-authorization is required, EXCEPT for part-time E2 airspace that changes to E4 whenever the adjacent control tower is open, i.e. the twenty or so airports described above.  This tends to suggest that the airspace within the dashed magenta line at KEGE and KFRI is not treated as E2 airspace when the tower is open, at least in relation to FAR 107.41.  However this doesn't really bear on whether this airspace still functions as some form of Class-E-to-surface airspace when the tower is open in relation to other FAR's.  One shouldn't read too much into the depiction on the LAANC map.
See also this related question: May an ultralight vehicle pass directly above KEGE at 9200 MSL at 1600Z with no prior authorization without violating FAR 103.17?
Are there any other airports where the airspace designations have been set up similar to KEGE and KFRI?

I am curious as to why you haven't contacted the FAA directly on this and the other related questions.

@MikeY-- I am currently waiting for a reply on one query, but stay tuned for more--

A more polite title might be "Is the Class-E-to-surface airspace near Eagle County Regional airport (KEGE) and Marshall AAF (KFRI) still in effect when the tower is open?" but I guess that would invalidate the existing answers wouldn't it--

The short answer is "No." The explanation: Class E airspace is not related to tower operations, it's related to ATC. In this case, the dashed area of the Class E is protecting the precision approach to runway 25. The surrounding shaded magenta area is the transition zone.

Well, I understand that, but things are a little weird in these two cases.  Contrasting these two examples with KENA in Alaska may be enlightening-- at KENA the "extensions" are designated as E4 w/ a note to see A/FD for effective hours, and are ALSO part of a chunk of airspace designated E2 that includes inner circle as well as the extensions w/ a note to see A/FD for effective hours.  The D also has a note to see A/FD for effective hours.  In that case the extensions would appear to clearly be E4 when tower is open and ratchet up to E2 when tower is closed.

Actually, the KENA case looks identical to the KUNV case. Not the normal way to do things, but they at least seem much less ambiguous (and less anomalous) than KEGE.  At KEGE are we really supposed to assume that when the tower opens, only the area in the dashed circle stops being E2, not the area out in the extensions, even though the whole chunk of airspace is delineated as one single unit of E2 on page E-170 of the Airspace Designations document?  If that would be accurate, wouldn't the same be true at KENA and KUNV?  But if it is, why even bother with the E4 designations at these 2?

I honestly think you are trying to find complication where there isn't any. Class E is about the specifics of operations around the field and in each case it may be different.

It appears that the best description of the airspace designations at KEGE and KFRI is that they exactly like the 21 other airports listed here What are all the US airports where E4 "extensions" change to E2 and become part of a larger E2 "surface area" when the tower closes for the night? , except that no E4 description has been provided to cover the area in the rectangular projection to the east during the time that the tower is open and the E2 airspace is not in effect.
Technically, as the descriptions have been written, it appears that there is no Class-E-to-surface airspace in the dashed magenta projections when the tower is open.
It's not clear whether this is an oversight (mistake), or whether the airspace planners simply made a presumption at KEGE and KFRI that all the E2 airspace would remain in effect 24/7 except for the particular portion that is superseded by the Class D when the tower is open.  In the latter case, it's not clear that that presumption is actually consistent with what was actually published in the "Airspace Designations and Reported Points" document.
At KEGE I've verified that local ATC treats the airspace as if there is Class-E-to-surface airspace in the projection to the east 24/7, and the same is surely true at KFRI.  Whether there has been a mistake in the airspace designations or not, it makes no sense for the airspace within the dashed magenta extensions at these airports not to be treated as Class-E-to-surface airspace when the control tower is open.
It would be interesting to know of any other airports where the airspace designations have been handled in this manner.

The airspace at KEGE has now been reconfigured, effective 03/26/20 (see 85 FR 2291.) The description may be found in the July 21, 2020 edition of JO700.11E. The footprint of the controlled-to-surface airspace has been considerably reduced. The E2 footprint is now identical to the (part-time) Class D footprint. The rest of the controlled-to-surface airspace is now covered by an E4 "extension", which is in effect 24/7. This is the most common way of handling Class D and Class-E-to-surface airspace at an airport with a part-time control tower. For another example, see KMFR. There are many more. –

No.  The Class E surface area is part of approach corridor for the instrument approaches into that airport so additional control and weather minimums are needed for this.  As such that block of airspace remains Class E 24 hours a day, whether the tower at KEGE is operative or not.

Then why, in the description of the E2 airspace in order 7400.11C (page E-171) https://www.faa.gov/documentLibrary/media/Order/JO_7400.11C.pdf , is there a note to see the A/FD for the effective hours?  (Read the whole question carefully.)  It seems to me that if the idea was that the E2 was meant to be in effect 24/7 , but for some limited portion of that E2 airspace to be automatically superseded by the Class D when the Class D was active, the note to see the A/FD for effective hours should have been only attached the Class D description, to avoid any ambiguity as to what happens to (ctd)

(Ctd) It seems to me that if the idea was that the E2 was meant to be in effect 24/7 , but for some limited portion of that E2 airspace to be automatically superseded by the Class D when the Class D was active, the note to see the A/FD for effective hours should have been only attached the Class D description, to avoid any ambiguity as to what happens to the outlying portions of the E2 when the Class D is in effect.

This airspace is a very odd case.  Was there any operational reason that they didn't just set it up the normal way, (example KMFR) where the outlying portions are described in the E4 section of JO 7400.11C with no notation about effective hours, while the inner circle has identical descriptions (except for altitude ceiling) in the Class D portion of JO 7400.11C and also in the E2 portion of JO 7400.11C, with a notice to see the A/FD for effective hours attached to each?  As far as I know KEGE is the only airport in the whole US whose airspace has been set up in this odd manner.

The answer above appears to address the operational reason why it would make sense to have Class-E-to-surface airspace near KEGE 24/7, but not to address the specific reasons raised in the original question (and comments above) as to why this interpretation is problematic.


text:
What are the historical precedents of today's E2 and E4 airspace? (US)
What are the historical precedents of today's E2 and E4 airspace?  From what previous airspace classes did these airspaces evolve?  How do these precedents help us understand the significance of the distinction between E2 and E4 airspace today?

What we now know as Class D and E2 airspaces were once (before 1992) a single type of airspace called a "Control Zone".  "Control Zones" first appeared on charts in the mid-1940's and consisted of a thin dashed circle enclosing an airport-- originally red, later blue. By the time of this 1974 test-prep publication, "Control Zones" had been defined to go up to the overlying "Continental Control Area" at 14,500' MSL.
Originally a "Control Zone" did not indicate a communications requirement for VFR traffic-- many non-towered airports had a Control Zone around them, and a few towered airports lacked them.  Instead, all towered airports were automatically assumed to have an "Airport Traffic Area" around them, 5 miles in radius and 3000' tall, that could not be entered without first establishing radio communications with the tower.  The purpose of a "Control Zone" was simply to impose-- all the way to the surface-- higher VFR cloud clearance and visibility requirements than would exist in "uncontrolled" airspace, for the protection of IFR traffic emerging from clouds.
Around September 1992, changes were made to the markings on the sectional charts in preparation for the upcoming September 1993 "alphabet" airspace reorganization, when the "Airport Traffic Areas" would disappear and the boundary of the communication requirement would be shifted to the edge of Class D airspace.  All "Control Zones" that did not contain a control tower had their depiction changed from a dashed blue line to a dashed magenta line, and were identified on the chart legend as a "Control Zone without communications requirement".  This was the immediate forerunner of today's E2 airspace.  At the same time, to eliminate the future communication burden on VFR traffic (and towers) that would be created in cases where Class D airspace had a projection extending far from a towered airport, some of the projecting portions of Control Zones at towered airports had their borders changed from dashed blue to dashed magenta and were identified on the chart legend as "Control Zone extensions".  These "Control Zone extensions" are the immediate forerunners of today's E4 airspace.  The complete legend on the charts for the new dashed magenta line was "Control Zone at airport without control tower and Control Zone extension without communications requirement".
It is interesting to compare aeronautical sectional charts dating from shortly before the introduction of the dashed magenta markings, to charts effective immediately after the introduction of the dashed magenta markings.  It is interesting to see how the Control Zones at airports with towers changed from their previous shapes. Some were made smaller. On some, any rectangular projections remained part of the blue dashed shape surrounding the airport, while on others, some or all rectangular projections were changed to magenta dashed lines that abutted against the blue dashed shape. The determining factor does NOT appear to simply be how far the projections projected away from the basic inner circular shape.  Clearly, planners were preparing for the communications requirement that would soon be shifted from the old "Airport Traffic Area" boundaries, to the edge of the Class D (or higher) airspace.
Note however that according to the FAR's, the "Airport Traffic Areas" still served as the boundaries of the communications requirement until the September 1993 "alphabet" airspace re-designation.
Therefore it's not clear to me whether or not the distinction between a "Control Zone" and a "Control Zone extension" had any actual practical or regulatory significance in the September 1992 to September 1993 time period.  Could it have simply been a charting convenience to help pilots, chartmakers, and others prepare for the regulatory changes that would go into effect in September 1993?
Certainly FARs 91.155c, 91.157a, 91.303c, 101.33a, and 103.17 continued to simply refer to "Control Zones" with no mention of "extensions" all the way up until the September 1993 airspace re-designation.  Would these FAR's have applied to airspace that was charted as a "Control Zone extension", or only to airspace that was charted as a "Control Zone"?
Diving a little deeper into this question of the significance of the distinction between a "Control Zone" and a "Control Zone extension" prior to September 1993: in the version of the FARs effective Jan 1993, we read "71.1 Applicability The complete listing for all jet airways, area high routes, Federal airways, control areas, control area extensions, area low routes, control zones, transition areas, terminal control areas, airport radar service areas, postive control areas, reporting points, and other controlled airspace can be found in FAA Order 7400.7A, Compilation of Regulations, dated November 2 1992."  Note the lack of the phrase "control zone extension" in this sentence.  Would a careful reading of the November 2, 1992 edition of FAA Order 7400.7A show that the airspace that appeared on the charts as a "Control Zone extension" was still simply considered part of a "Control Zone" from a regulatory standpoint?  Does the phrase "Control Zone extension" appear in this edition of FAA Order 7400.7A at all, or was that airspace simply treated as a completely integral part of the adjoined  "Control Zone"?  So that the distinction between "Control Zone" and "Control Zone extension" essentially existed on the aeronautical charts only, and nowhere in the actual regulatory documents?  I haven't yet been able to obtain a copy of the November 2, 1992 edition of FAA Order 7400.7A, and don't know the answer to these questions.
The actual transition from the "Control Zone"/ "Control Zone extension" terminology to the modern "alphabet" terminology happened in September 1993.  At this time "Airport Traffic Areas" ceased to exist, and all the airspace surrounded by a dashed blue line on the sectional became Class D airspace, and all the airspace surrounded by a dashed magenta line on the sectional became Class E airspace that extended all the way to the surface.  This is when the awkward terminology that we currently find used to describe E2 and E3/E4 airspace in the "Airspace Designations and Reporting Points" document was first applied to what had previously been depicted on the charts as "Control Zones" (around non-towered airports), and what had previously been depicted on the charts as "Control Zone extensions", respectively.  Considering that E4 airspace also goes all the way down to the surface, it's unfortunate that someone didn't come up with a better term than "Designated as Surface Areas" or "Designated as a Surface Area for an airport" to describe the E2 airspace.  September 1993 is also when the language of FARs 91.155c, 91.157a, 91.303c, 101.33a, and 103.17 was changed to its current awkward form.  Regardless of whether or not these FARs had been considered to apply to the airspace of the "Control Zone extensions" during the year or so that they were labelled in that manner on the charts, the language adopted for those FARs in September 1993 clearly matched the E2 airspace description in the "Airspace Designations and Reporting Points" document effective at the time (as well as at the present), and did not match the E3/E4 airspace description.
Addendum--
As a point of related interest, here is a list of activities that require prior authorization (or in the case of aerobatic flight, are prohibited) in E2 airspace but not E3/E4 airspace, along with the relevant FAR or other legislation:
Operating VFR without a SVFR clearance in certain adverse weather conditions -- FAR 91.155c
Ultralight flight-- FAR 103.17
Aerobatic flight-- FAR 91.303c
Operation of an unmanned free balloon below 2000' AGL-- FAR 101.33a
Operation of a small Unmanned Aerial Vehicle (e.g. commercial drone) -- FAR 107.41
Operation of a recreational small Unmanned Aerial Vehicle (e.g. typical hobbyist drone or model airplane) under the "Recreational Exemption" -- language passed by Congress in October 2018
Also, FAR 91.157a allows ATC to grant a SVFR clearance in E2 but not E3/E4
As noted in the links below, the distinction between E2 and E3/E4 airspace is not always observed by ATC in actual practice in relation to the requirement for, and the possibility of granting, a SVFR clearance.
Sources--
Source for FARs as they existed in January 1 1993, also listing the modifications that would become effective September 16 1993
Source for dimensions of "Airport Traffic Area"
Related content on ASE--
What are E2 and E4 airspace?
What are E2 and E4 airspace?
What are E2 and E4 airspace?
Which parts of class E airspace can an ultralight (part 103) fly in without prior ATC authorization?
Does an SVFR clearance extend to Echo surface extensions?
Does an SVFR clearance extend to Echo surface extensions?
Does FAR 91.155c apply to class E surface extensions?
In actual practice, do ARTC Center personnel generally follow the rule that a SVFR clearance may be granted in E2 airspace but not E4 airspace? (US)
In the US, is there much variation among the various ARTC Centers as to where a SVFR clearance may be granted?
How does the distinction between E2 and E3/E4 airspace affect pilots?

Why did you pose the question if you already knew the answer?

To create a place to post the content that helps support another answer I recently posted, which by the way was in response to someone else's question, not mine.  But let me know if you think I'm abusing ASE.

No no.  Good answer.  I was just curious.

@quiet flyer, if I ever have a question about E2 vs E4 airspace I know who to come to!  Man, you are on a serious quest these days, mind if I ask what's driving all this?

Would it be possible to summarize succinctly how a distinction between E2 and E4 affects pilots?

@MichaelHall-- now the information you asked about has been added as an addendum to this answer.

@MichaelHall -- Now also as a separate answer to a new question-- maybe I should remove the addendum from this answer now--

This answer is very much in need of revision.  For one thing, it's certain that the control zone "extensions" that appeared on the aeronautical charts in the October 1992 to September 1993 time period were only there to prepare pilots for the upcoming September 1993 changes-- before September 1993 a control zone "extension" was simply part of the adjoined control zone from a regulatory standpoint, even if the chart markings seemed to suggest otherwise.  Expect a substantially revised version of this answer in the near future.

Also, as may be apparent from the related answer https://aviation.stackexchange.com/a/75022/34686 , I've retreated from the position that phrases like "within the lateral boundaries of the surface area of Class E airspace designated for an airport" unambiguously exclude E4 airspace.  That's certainly what the "Airspace Designation and Reporting Points" document seems to suggest, but there's another FAR that seems to suggest otherwise.  Will be addressed in revision.


text:
To what FAA office or personnel should one direct an inquiry about the reasons behind the airspace design at a particular airport?
The airspace design process is extremely complex.  See for example this FAA document, Order 7400.2M.
To what FAA office or personnel should one direct an inquiry about the reasons behind the design of the airspace around one particular airport?
I'm seeking real-world, practical insight as to why the unusual airspace configuration we see at KACV and KTVL was selected, over the common configuration that we see for example at KONP and KCEC.
I'm specifically seeking information about why the airspace was designed that way, not about how it is being handled now in actual practice by ARTCC etc.
These two airspaces are rather unusual and it's unlikely that a satisfactory answer will be obtained just by perusing the FAA documents giving general guidance on how to design airspace to handle existing/ proposed instrument procedures, etc.
However any kind of actual "paper trail" relating to the design of the airspace at these two particular airports could possibly be helpful, if it were not too "dense" to interpret -- how might that be obtained?
But I'd prefer to speak to an actual person, if he/she had some relevant insight on the design process for the airspace at either of these airports.
Although guidance concerning my specific case is most welcome, also I'm seeking an answer crafted in such a way as to be helpful to anyone seeking  to answer a similar question for any airport in any region of the nation-- how to go about locating an appropriate person or FAA office to direct such a query toward?

I just looked at a chart and I don't see anything particularly unusual about the airspace around KACV and KTVL.  What is it about that particular configuration that puzzles you?

https://aviation.stackexchange.com/questions/63970/what-is-the-primary-reason-that-the-non-towered-airports-kacv-and-ktlv-have-e4-e

Compare and  contrast  the 4 examples listed in question, then see additional link above-

By reading your linked FAA Order and finding references for responsible offices and a little follow-on search, I found this link to the Office of Mission Support within the Air Traffic Organization.
Airspace analysis appears to be within their purview:

Mission Support Services oversees the Air Traffic Organization’s
  activities in:

Aeronautical Information Manual (PDF)
Aeronautical Information Services
Air Traffic Organization Environmental Reviews
Air Traffic Procedures Advisory Committee (ATPAC)
Instrument flight procedures production/charting
Metroplex
New York/New Jersey/Philadelphia Airspace Redesign
Obstruction Evaluation/Airport Airspace Analysis (OE/AAA)
Performance-Based Navigation (PBN) Implementation And Usage Dashboard
Pilot Web

They provide the following contact information:

Address
  FAA National Headquarters
  1028 - 10A
  800 Independence Ave., SW
  Washington, DC  20591
Phone: (202) 267-8261

You can try the local FSDO as that is generally a decent place to start but the FAA is under no obligation to tell you why they do things the way they do.
You may also want to ask around at your local airfield. One of the guys that worked on the KPHL Bravo flys out of the little field I trained on. I met him one evening at an EAA meet up and he told me all kinds of stories about why they made the airspace the way they did. He was not/is not an FAA employee and was on some kind of committee that was put together to design it. You may have luck finding people who had input on the airspace just by asking around.


text:
In the US, in actual practice, workload permitting, will ARTC facilities grant SVFR clearance for surface-level Class E "extensions" (E4 airspace)?
In the US, in actual practice, workload permitting, will ARTC Centers and Approach Control facilities grant clearance for Special VFR operations in surface-level Class E "extensions" (E4 airspace)?
Does the answer vary between different ATC facilities?

@atc_ceedee -- since you have recently answered several other atc questions, perhaps you'd considering posting an answer here if you have any specific examples from your own experience (and I seem to recall from another recent comment that you said you did-- ) (but would need to be from after the 1993 "alphabet" re-designation to be relevant)

@atc_ceedee -- never mind, you already did-- (see link below).  It would not be inappropriate to post / adapt that as an answer to the present question too though.

Highly related -- https://aviation.stackexchange.com/a/86975/34686

In the US, in actual practice, will ARTC Centers and Approach Control
facilities grant clearance for Special VFR operations in E4
surface-level Class E "extensions"?

Some will, and some won't.

Does the answer vary between different ARTC facilities?

Yes.
Note the range of comments below obtained from questions posed by telephone in May 2019 to various ARTC Center and Approach Control staffers-- in most cases, the "Watch Officer" on duty, or else an "Airspace Specialist"--
(The summaries below are based on written notes and are not verbatim transcriptions.  The actual airspace descriptions are not from the staffers but rather are from the FAA's "Airspace Descriptions And Reporting Points" document, JO 7400.11E.)
Note also that in no case did the staffer indicate that the specific reason that SVFR would not be approved for an surface-level Class E "extension" was because it was designated as E4 airspace rather than E2 airspace.  Airspace definitions for some airports are actually written so that the surface-level Class E (E4) "extensions" convert to E2 surface-level Class E airspace when the control tower is closed, but no staffer ever indicated that that change in status would have any effect on whether a Special VFR clearance might be granted for that airspace.  Several staffers were not even aware that surface-level Class E airspace was broken down into several different subcategories (e.g. E2 versus E3/E4) in the FAA's "Airspace Designations and Reporting Points" document.
Facility-- Harrisburg Approach (PA)
Airport: KLNS-- Lancaster-- PA
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level Class E (E4) "extension" to SE, converts to surface-level Class E (E2) when tower closes.
Staffer stated that when tower is closed, Harrisburg Approach may issue SVFR clearance for the entire "surface area", which does include the airspace in the "extension", because it  goes down to the surface, whether the tower is open or closed.  In response to my questioning, said it has nothing to do with whether the airspace is E2 or E4-- it's all "Echo" to them.  Said tower is only authorized to issue SVFR clearance for the Class D airspace, but if tower contacted Harrisburg Approach with a request, odds are good a SVFR clearance could be granted for the E4 extension as well.  Stated tower has to call Harrisburg Approach anyway when granting a SVFR clearance so it would not be a burden to ask.  Noted that S37 is within the E4 extension so a pilot flying from KLNS to S37 might have good reason to want a SVFR clearance including the extension.

Facility-- Seattle Center ARTCC
Airport-- KACV-- Arcata CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extension" to SE effective 24/7, depicted as separate areas on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area.  In response to my questioning, stated made no difference whether the airspace was E2 or E4.

Facility-- Salt Lake City ARTCC
Airport-- KSHR --Sheridan County-- WY
Airspace description-- surface-level Class E (E2) airspace, effective 24/7, extends far to NW and SE of airport
Staffer's initial response was that a SVFR clearance would be limited to a certain radius from the airport such as 5 miles, but after taking a closer look at the sectional chart said a SVFR clearance could indeed include the entire Class-E-to-surface area.  Stated that since the area is quite large, let ARTCC know if you only need the northern part or the southern part.
The staffer also offered opinions on the airports below, while noting that they are not actually in the Salt Lake City ARTCC area of responsibility--
Airport-- KBIH -- Bishop-- CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extensions" to N effective 24/7, all depicted by a single dashed magenta line on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area. In response to my questioning, stated made no difference that extensions were E4 not E2.
Airport-- KTVL-- South Lake Tahoe-- CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extension" to N effective 24/7, depicted as separate areas on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area.  In response to my questioning, stated made no difference that extensions were E4 not E2.

Facility-- Minneapolis ARTCC
Airport-- KSTC-- St. Cloud MN
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level Class E (E4) "extension" to SE, converts to surface-level Class E (E2) when tower closes.
Staffer stated that tower could only issue a SVFR clearance for the Class D airspace, but if tower were closed and pilot contacted Center, a SVFR clearance might be able to include the extension to SE.  Wasn't sure about this, said no one had ever asked.  Noted that there is small airport just inside the far end of the extension so there might be reason to desire such a clearance.  Was unfamiliar with designations E2 and E4 and planned to do more research on the topic.

Facility-- Oakland Center
Airport-- KBIH-- Bishop CA
Airspace Description-- surface-level Class E (E2) circle 5 miles in diameter around airport effective 24/7, surface-level Class E (E4) "extensions" to north effective 24/7, all depicted by a single dashed magenta line on the sectional chart--
(Staffer indicated that the above description was only valid for the winter season.  Stated that the summer configuration was class G up to 1200 feet.  That has apparently now changed, as the 2-25-21 Chart Supplement simply says "AIRSPACE: CLASS E")
Regarding the winter configuration, staffer said a SVFR clearance would not be granted beyond 5 miles of the airport because the purpose of a SVFR clearance is just to get pilots up away from the airport or down into the airport, and the terrain to the north is mountainous so they don't want pilots flying SVFR there.  Also stated that the purpose of the extensions is to facilitate instrument arrivals and departures so they wouldn't want pilots flying SVFR there.  Said even in a case where terrain were flat they likely would not grant SVFR beyond a certain radius from the airport conforming to the basic inner Class D or Class-E-to-surface circle, because the extensions are to facilitate instrument arrivals and departures.  In response to my questioning, said it had nothing to with whether the airspace in the extensions was E2 or E4.

Facility-- Kansas City ARTCC
Airport-- KTOP-- Phillip Billard near Topeka KS
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level (E4) "extension" to SE effective 24/7.
Staffer stated that a SVFR clearance could not include the extension because the purpose of a SVFR clearance is just get to pilots up away from the airport or down into the airport and if you can't do it within the D circle you should file IFR or not fly.  Stated that the purpose of the extension is to protect IFR traffic, so they wouldn't want to issue a SVFR clearance there.  In response to my questioning, stated made no difference that the airspace in the extension was E4 rather than E2 -- they just call it "Echo" and don't make that distinction.  Comments were not specific only to KTOP but also stating the general principle involved.

In essence, whether or not SVFR clearance will ever be granted by ARTC for a specific chunk of surface-level Class-E airspace that projects some distance from the basic circle of surface-level controlled airspace around an airport, seems very much to depend on the "culture" of the particular ARTC Center involved, as well as factors such as terrain hazards specific to the particular geographic location involved.

Note that the related answer Does an SVFR clearance extend to Echo surface extensions? quotes a 2010 letter from the FAA ATO Western Service Center stating that their opinion is that the FARs do not permit SVFR to be authorized in E4 surface-level Class E "extensions".  The original query that provoked the answer was apparently specific to KSTC, an airport where all the surface-level controlled airspace reverts to Class G airspace when the tower is closed, so all requests for SVFR would always be directed to the tower, and ARTC would not be used to receiving any requests for SVFR for any of the airspace associated with that airport during the hours that the tower was closed.  Yet the letter is phrased more broadly and indicates as a general principle that SVFR should not be permitted in any E4 surface-level Class E "extensions".
Clearly, not all ARTC facilities follow this guidance.

See these other related ASE questions and answers--
Does FAR 91.155c apply to class E surface extensions?
What indication has the FAA given that phrases like "surface area of Class E airspace designated for an airport" do or don't include E4 "extensions"?
What are the historical precedents of today's E2 and E4 airspace? (US)
Which parts of class E airspace can an ultralight (part 103) fly in without prior ATC authorization?

This answer would benefit from adding screenshots of the sectional charts for the relevant airspaces.  Stay tuned...

Highly related -- https://aviation.stackexchange.com/a/86975/34686

Update -- at KTVL the surface-level Class E "extension" has now been deleted.  At KACV the airspace configuration has not changed but the boundary between the E2 circle and the E4 "extension" is no longer depicted on the sectional chart.

New related content has been posted here -- https://aviation.stackexchange.com/a/55806/34686 .  Some of that content would also fit well in this answer as well.

I need to edit this answer to show screenshots of the airspace configurations as they appeared on the sectional charts at the time that this answer was written.

Add the following text: Here's an excerpt from another ASE answer ( https://aviation.stackexchange.com/questions/71406/in-the-us-how-does-the-distinction-between-e2-and-e3-e4-airspace-affect-pilots/86975#86975" ), authored by an Air Traffic Controller, that takes the same view: (of no distinction between E2 and E4)
"In the Center environment, we make no distinction between the surface area and the extensions when dealing with SVFR."


text:
What is missing from these diagrams of the forces in slips and skids?

See these images that are widely reproduced in many different on-line ground school materials.
A) Is the magnitude of the wing's lift vector illustrated correctly in each of the three cases?  Should it really be the same size in each case?
B) What real aerodynamic force generated by the aircraft has been completely omitted from the second two cases, but should be included to make the diagrams more comprehensible?  Specifically, to explain why the vector labelled "load" is not the same in all the figures?
Assume that the aircraft is maintaining a constant altitude and airspeed regardless of whether the turn is coordinated, slipping, or skidding.
(The same diagrams could apply to gliding flight as well, in which case we would assume that the aircraft was maintaining a constant airspeed and a constant descent rate in relation to the surrounding airmass.)
The intent of the question is to address a major flaw in the diagrams, not to nitpick small errors on the part of the artists.  The second diagram is the best one to focus our attention on, because the bank angle is clearly drawn to be identical in every case, and the horizontal and vertical components of the lift vector are clearly drawn to be identical in every case.
A word about the images included here-- both images are widely reproduced in many different on-line ground school materials.  For example, the first image appears as Figure 3-21 from this "Aerodynamics in Flight" section from an on-line ground school.  For another example, see page 12 of this document.  It may have originally been published in the FAA's "Pilot's Handbook of Aeronautical Knowledge".  The second image appears as figure 5-35 on page 5-24 of the FAA's "Pilot's Handbook of Aeronautical Knowledge" (2016 edition).  It also may be found in various on-line ground school materials-- see for example this one.

I think it is very incomplete because you have to consider force vectors introduced by the sideways fuselage orientation and the offset thrust line.  This means in the slipping turn you have lateral forces acting on the fuselage and the thrust line acting outward on the lateral axis, and vice versa for skidding.  Now to quantify that, not sure.

Let us continue this discussion in chat.

Please don’t cross-post almost exact questions across the network.  Either this question or the one on Physics should be deleted.

@dalearn -- I am considering what to do next -- I do not intend to delete the one from ASE but maybe will delete the other one -- https://physics.meta.stackexchange.com/questions/12902/should-i-migrate-an-answer-to-another-se-site

Sorry about the late reply.  I don’t have a specific meta discussion relating to this to point you to but in general, the culture of SE as I have observed, is that cross-posting is discouraged in many cases.  This question would be a good question for either Physics or Aviation but given the reception at each site, I recommend deleting this one.

Perhaps someone with more knowledge of meta could point to an official discussion about the cross-posting issue.

If it becomes clear that the ASE community is strongly offended by having a similar question on PSE, then I will delete the PSE one (after "importing" the PSE answer to the present question), but my preference is to chalk it up to experience and leave it alone.  I will avoid asking similar questions in different SE forums now that I understand it is frowned upon.  For more see https://physics.meta.stackexchange.com/a/12906/236723. If someone really wants to make a case that the ASE question should be closed or deleted if the PSE one is not, perhaps they should open a discussion on ASE meta.

A) Is the magnitude of the wing's lift vector illustrated correctly in
  each of the three cases? Should it really be the same size in each case?

No (on both counts).

B) What real aerodynamic force generated by the aircraft has been
  completely omitted from the second two cases, but should be included to
  make the diagrams more comprehensible? Specifically, to explain why the
  vector labelled "load" is not the same in all the figures?

Side-slip.

This is my attempt at better describing the forces in a slipping, skidding and coordinated turn. These thoughts represent my best guess and should be considered the basis for further discussion rather than fact.
The biggest and somewhat major limitation of my diagram (that I'm aware of), is that it doesn't show the critical role of yaw (due to my limited ability to draw, rather than by design).
Ideally it would show a yaw away from the turn for a slip and a yaw toward the turn for a skid.
This would also serve to clarify that the aircraft depicted is viewed from behind (only relevant to the slip ball displacement shown).
Another limitation of the diagram, due to it's 2D nature, is that it doesn't illustrate conventional drag (along the longitudinal axis) and how it varies with yaw during a slip or skid. ie: the force acting perpendicular to and out of the screen. This is important as the vector diagram doesn't facilitate conceptualising total drag during uncoordinated flight.
The key to understanding slipping, skidding and coordinated turns (as I understand it), is recognising the effect of side-slip on the total aerodynamic force (TAF) which is defined as the net aerodynamic force experienced by the aircraft. As per the previous paragraph, this diagram only considers the TAF along the lateral axis and so doesn't provide the complete picture, though it does serve to fully explain the different turn rates and resulting turning radii.
To be clear, I'm using the term side-slip to refer to the aerodynamic condition where an aircraft has an asymmetrical airflow about it's longitudinal axis resulting in a degree of lateral motion with respect to the relative airflow.
The air impinging on the exposed side of the aircraft effectively creates a lateral force, which is labelled side-slip in the diagrams.
The diagram depicts forces on the basis that, regardless of whether the turn is coordinated, slipping, or skidding - the aircraft is maintaining a constant;

angle of bank; and
altitude (thus lift [$TAF_{vertical}$] always equals weight); and
airspeed

This means the main variables are;

AoA (power) - indirectly represented by the vector labelled TAF

Quick recap on the aerodynamics of a turn:

In any turn (assuming the constants above), the power requirements increase
proportional to the rate of turn.

In vector speak, a turn is achieved by tilting the TAF away from the vertical
in the direction of the turn. The resulting horizontal component provides the
centripetal acceleration required, thus the greater the tilt, the
greater the rate of turn.

The consequence of tilting the TAF away from the vertical is a reduction in
lift. In order to maintain altitude during a turn, the TAF must therefore be
increased in order to keep the vertical component equal to what it was in
level flight. This represents an increased power requirement.

In the diagram, the length of the TAF vector varies in each scenario, therefore each has a different power requirement.
For any given side-slip angle (representing a given amount of drag along the longitudinal axis), a skidding turn requires more power than a slipping turn due to the higher value of $a_c$. I am making the assumption that the lateral drag is the same in both cases (but I don't know if this is the case).
I posit that at some angle of side-slip, the power required for a slipping turn will exactly equal that required for a coordinated turn. In this scenario, some of the power used to create the turning force ($a_c$) during a coordinated turn is instead used to combat the additional frontal drag associated with a slipping turn, which results in a reduced rate of turn.
It seems a skidding turn does a better job at turning than a coordinated turn. This is true, the rate of turn is higher, so why not use a skidding turn to turn faster than a coordinated turn? Aerodynamic hazards aside, it's simply less efficient.
Key to realise is that the rate of turn achieved per unit of power (ie: efficiency) is less in an uncoordinated turn (slip or skid) as power is wasted in both dragging the aircraft sideways and forwards (additional drag is created in the direction of travel as the aircraft presents a greater cross-section to the relative airflow).
Thus, in order to achieve a given turn radius, it is more efficient (requires less power) to perform a coordinated turn at a higher angle of bank than a skidding turn at a lesser angle of bank or a coordinated turn at a lower angle of bank than a slipping turn at a higher angle of bank.

turn radius
The turn radius is determined by nothing other than the horizontal component of the TAF, identified as $a_c$ in the diagrams.
A higher centripetal acceleration results in a smaller turn radius and a lower centripetal acceleration results in a larger turn radius.

Insights:

the TAF varies according to how coordinated flight is, in order to keep the value of lift ($TAF_{vertical}$) constant (ie: to maintain altitude in the turn)
apparent gravity / load and how it changes is explained simply as the reaction force equal and opposite to the varying TAF (rather than a result of centripetal force and it's fictitious sibling centrifugal force)
in a level slipping turn, side-slip opposes the horizontal component of lift ($a_c$) increasing the radius of the turn
in a level skidding turn, side-slip reinforces the horizontal component of lift ($a_c$) reducing the radius of the turn

Comments & criticisms welcome.

I think your diagrams would be more accurate if you deleted the vector labeled "lift", and applied the label "lift" to the unlabeled vector that is aligned with the vertical fin. (In the coordinated turn, this is also the same as the vector labeled total aerodynamic force, but not in the other cases.) But even then I think the diagrams would contain a small error. But they would be much better than the FAA diagrams, because they do include the vectors representing the aerodynamic sideforce generated by the sideslip or skid.

There is a paradox that seems to be raised by this answer (which I suggest would not be raised if the diagrams were drawn completely correctly.) The paradox is this: if the lift vector generated by the wing is the same in every case, and the aerodynamic sideforce vector is no larger in the skid than in the slip, then why should the skid require more power than the slip, to maintain power at a given bank angle, as this answer seems to suggest?

Another thing to keep in mind is that the drag vector does not appear in the diagram at all, because it acts parallel to the flight path and so would point straight away from the viewer, assuming that the flight path is intended to be aimed straight toward the viewer, i.e. straight out of the page. (Yes, as you point out, ideally the aircraft should be drawn yawed a bit to one side or the other in the slip and the skid.) Presumably power is applied as needed to balance drag, so that airspeed and altitude can both stay constant. Doesn't generating the aerodynamic sideforce incur a drag (ctd)

Doesn't generating the aerodynamic sideforce incur a drag penalty? Just because it is not illustrated, doesn't mean it doesn't exist. So the statement that a slipping turn requires less power to maintain altitude than a coordinated turn needs to be reconsidered. Do you mean for a given bank angle, or for a given turn rate (radius)? I would argue that the latter statement would certainly not be true, while the former statement would be true for extreme bank angles but not for shallow bank angles -- the exact bank angle at which it would become true would depend on (ctd)

I would argue that the latter statement would certainly not be true, while the former statement would be true for extreme bank angles but not for shallow bank angles -- the exact bank angle at which it would become true would depend on how efficient the aircraft was at generating aerodynamic sideforce, but it would certainly be true for all aircraft by the time the bank angle reached 90 degrees. Even infinite power won't allow a 90-degree bank angle to be sustained in a fully coordinated turn with no loss of altitude.

Whereas "knife-edge" flight at 90-degrees bank is a classic airshow maneuver, and is an example of sideslip taken to such an extreme that the turn rate is zero and the turn radius is infinite.

@jumblie like your diagrams.  Try drawing them with the same gravity and centrifugal loads (from the earth reference) and put the plane at different angles relative to the horizon/earth surface.  (This is how a "ball" inclinometer actually works).  Any object moving in a horizontal circle of the same radius at the same speed will have the same combined load vector.  How the plane creates force to counteract these loads is different for skid, coordinated, and slip.  Note in the skid, the less efficient prop, instead of the more efficient wing, is used to "pull" the plane around.

@quietflyer Thanks for the feedback, better than the current FAA diagrams isn't really much of an accomplishment! I have updated my answer to address most of the points you raised. Whilst it is important, we can discuss the semantics of labels later, getting the fundamental concepts right is my focus right now. Hopefully it is now evident why a skid requires more power than a slip - you're turning more! I've addressed the additional drag associated with uncoordinated flight and introduced the concept of efficiency too to make this clearer. Let me know if I missed anything.

@RobertDiGiovanni Thanks, I think they're a step in the right direction. I purposefully kept the angle of bank constant as per the original question. I'm actually a rotary wing guy so I've tried to keep it as generic as possible - not exactly sure at what stage ignoring the differences between fixed and rotary wing will get us into trouble.

@jumblie  guess it's like trying to make a 3 legged stool work.  You don't "get into trouble" being rotor because any turn of a given radius and velocity will produce to same Gravity and "centrifugal force" loads on an inclinometer.  In a car you have to build a suitable bank to "center the ball", in the air simply banking into the turn will do it.  "Coordinated" is simply the lowest drag configuration to turn.  draw the circle, earth referenced first .  You will see the skid, coordinated, and slipping are at different bank angles WRT the gravity vector.

Re "Whilst it may seem counter-intuitive that a slipping turn uses less power than a coordinated turn, it's because you're getting less centripetal acceleration. ie: yes, you're using less power, but you're also turning less." -- so you are saying that if you are established in a coordinated turn at constant altitude, and then you apply top rudder to introduce sideslip while manipulating the other controls as needed to hold bank angle and airspeed constant (but you don't touch the throttle), you'll end up in a sustained climb?

And likewise that if you are established in a coordinated turn at constant altitude, and then you apply top rudder to introduce sideslip while manipulating the other controls as needed to hold bank angle and altitude constant (but you don't touch the throttle), you'll end up at a higher airspeed?  Might be grounds for another ASE question if you really believe this to be true, so we can all post our differing answers.  But what you are missing is the extra drag created by flying the fuselage sideways through the air.

PS actually it is indeed true that introducing sideslip can reduce the sink rate for a given bank angle, or allow an aircraft to climb at a faster rate for a given bank angle, or allow an aircraft to maintain altitude at a given bank angle with less power -- but only if the bank angle is very steep.  Again see the example of knife-edge flight in my comments of two days ago.  But this answer says it is true in general.  If it were true in general, the  typical forward slip that we use to steepen a landing approach wouldn't have the desired effect at all.

@quietflyer Thanks for making me see the light! A victim of tunnel vision, I failed to consider the dynamics in all but the lateral direction. Answer revised. I've also clarified that I'm not intending to present my thoughts as fact. Perhaps chat would be a more appropriate forum? I engaged with this question not because I believe I have all the answers but because the existing material on this topic leaves a lot to be desired and I believe that as a community we can do and should strive for better.

Yes, chat would no doubt be more appropriate. I'm surprised that the system hasn't already asked us if we want to continue the conversation in chat; if it does, say yes.  That will automatically copy the past comments into the new chat room.

By including the vector labeled "centrifugal force", the illustrators have signalled that they are basing their reference frame on the aircraft itself, not the earth or the airmass.
The reference frame based on the aircraft is not a valid inertial reference frame.
The aircraft cannot accelerate with respect to itself.  The net force in the aircraft's own reference frame must be zero.  Yet that's not what we see illustrated in the diagrams for the "slipping" and "skidding" cases.
It would better to omit the "lift" vector entirely and just show the load vector, weight vector, and "centrifugal force" vector, than to give the false impression that the actual aerodynamic forces generated by the aircraft are identical in all three cases.
What is missing from the "slipping" and "skidding" diagrams is the aerodynamic sideforce generated by the fuselage as it flies sideways through the air.  When this vector is added to the lift vector, we end up with a net aerodynamic force vector that is equal in magnitude and opposite in direction to the vector labelled "load".
To make this work, the lift vector must be reduced in size in the slipping case, and must be increased in size in the skidding case.
Drawn this way, the diagrams would help the reader to understand the real reason why the inclinometer ball is displaced to the side in a slip or a skid.  Fundamentally, it is due to the aerodynamic force created by the airflow striking the side of the fuselage.  As a result, the net aerodynamic force vector is no longer "straight up" (i.e. parallel to the vertical fin) in the aircraft's own reference frame.  So the ball, and the pilot's body, and the other aircraft contents, tend to be displaced toward the low wingtip in a slip, and toward the high wingtip in a skid.
Drawn correctly, the diagrams would teach the reader this concept, regardless of whether or not the choice is made to include the "centrifugal force" vector or not.
Drawn correctly, the diagrams would also teach the reader that the load "felt" by the airplane, slip-skid ball, pilot's body, etc, is the direct result of the aerodynamic forces generated by the aircraft.  The "load" vector must always be the mirror image of the net aerodynamic force vector.
Drawn correctly, the diagrams would help the reader understand why increasing or decreasing the lift force by moving the stick or yoke forward or aft during a normal coordinated turn doesn't make the slip-skid ball deflect toward one side or the other, even though the turn rate is altered.  As long as the net aerodynamic force vector acts straight "up" in the aircraft's reference frame, the apparent "load" vector must act straight "down" in the aircraft's reference frame, regardless of whether the turn rate is "right" for the bank angle and airspeed, or has been temporarily boosted or decreased via a pitch control input.  (Naturally, such variations in the lift force will also cause the flight path to curve skywards or earthwards-- for a given bank angle, there's only one value for the lift vector that permits a stabilized turn at constant airspeed.)
Starting from the "load" vectors that we've been given here, what would the corrected diagrams look like?  They would look like the top row of diagrams described in the remainder of this answer.
Diagrams to be added-- for now we'll have to use our imagination.
I'm referencing the second diagram specifically, the one from the 2016 edition of the "Pilot's Handbook of Aeronautical Knowledge", where the aircraft are clearly all drawn at exactly the same bank angle.
Imagine four rows of diagrams, each based on the diagram referenced above, but modified as follows--
First row -- forces in aircraft reference frame (not a valid inertial reference frame)
Weight and "centrifugal force" and "load" as illustrated in original.  Note that "load" is the vector sum of weight and "centrifugal force".
The figures will include a net aerodynamic force vector (not shown in original).
 The net aerodynamic force vector must be exactly equal and opposite to "load" in all three figures.
Lift vector is correct in fig 1 of original (coordinated), and same as net aerodynamic force.  So fig 1 of first row of answer is essentially same as original.
Lift vector needs to be shorter in fig 2 (slip), and there needs to be an aerodynamic sideforce vector acting at right angles to the lift vector, pointing to the right side of the page and upwards.  That is the force that is missing from the diagram.  It is generated by the air hitting the side of the fuselage.  The vector sum of lift plus sideforce is the net aerodynamic force vector, and it must be exactly equal and opposite to the "load" vector.
Lift vector needs to be longer in fig 3 (skid),  and there needs to be an aerodynamic sideforce vector acting at right angles to the lift vector, pointing to the left side of the page and downwards.  That is the force that is missing from the diagram.  It is generated by the air hitting the side of the fuselage.  The vector sum of lift plus sideforce is the net aerodynamic force vector, and it must be exactly equal and opposite to the "load" vector.
With the figures drawn this way, we are able to see that we actually "load up" the wing in a skid, in the sense that we force it to create more lift than we'd normally need for a given bank angle, assuming that we are not letting the flight path curve earthward.  The turn rate is also increased, and the turn radius is decreased.
(On the other hand, if we hold the turn radius fixed and leave the bank angle unconstrained, then a skid actually "unloads" the wing, because it involves a shallower bank angle.)
Second row-- forces acting on aircraft in earth reference frame (or in the reference frame of airmass moving at constant speed)--(these are valid inertial reference frames, at least from an elementary viewpoint that views gravity as a real force.)
Same as above but "centrifugal" force and "load" are omitted.  A net force vector may be added which is the vector sum of net aerodynamic force and weight.  It is horizontal, and exactly equal and opposite to the (omitted) "centrifugal force" vector.  It is the centripetal force vector that causes the turn.  For a given bank angle, it is smaller in the slip, and larger in the skid, than in coordinated flight.
Third row-- aerodynamic forces only-- same as above but now weight is also omitted.  Now there is less clutter to take our attention away from the net aerodynamic force vector.  Note that the net aerodynamic vector is aligned with the aircraft's sense of "up" (i.e. the direction of the vertical fin is pointing) in coordinated flight, but not in the slip or skid.  This is arguably the most important row of diagrams.  It shows us what the pilot really "feels".
Or if it makes more sense to us-- we can have a fourth row-- "apparent inertial force" "felt" by the pilot-- exactly equal and opposite to the net aerodynamic force vector on row 3.  Just this one force vector for each figure, with all aerodynamic forces omitted.  It is valid to say that this apparent inertial force is caused purely by the net aerodynamic force vector.  It is also valid to note that it is exactly equal to the vector sum of gravity and "centrifugal force", though those won't be included on the fourth row of diagrams.  It is also valid to observe that the "apparent inertial force" vector is exactly the same thing as the vector labelled "load" in the top row of diagrams.
Unlike the diagrams in the question, the diagrams in the answer won't show the wing's lift vector decomposed into horizontal and vertical components.  No real insight is provided by doing that, especially when we completely omit the aerodynamic sideforce vector generated by the airflow hitting the side of the fuselage.
Unlike the diagrams in the question, the diagrams in the answer won't give the illusion that somehow the net aerodynamic force vector is "balanced with" (equal and opposite) the load vector, or the vector sum of weight and centrifugal force, in the coordinated turn, but not in the slip or the skid.  That is simply not true.  The load vector is equal and opposite to the net aerodynamic force vector in all three cases.  From one point of view, the net aerodynamic force vector is what causes the load vector.
Unlike the diagrams in the question, the diagrams in the answer won't give the illusion that the "centrifugal force" vector is exactly "balanced with" (equal and opposite) the horizontal component of the net aerodynamic force vector in the coordinated turn, but not in the slip or the skid.  Again, that is simply not true.  The "centrifugal force" vector is equal and opposite to the horizontal component of the net aerodynamic force vector in all three cases.  Because fundamentally, in this specific case where the vertical component of acceleration is constrained to be zero, we can observe that the centrifugal force vector is entirely caused by the horizontal component of the net aerodynamic force vector.
Unlike the diagrams in the question, the diagrams in the answer won't give the false impression that some mysterious thing, presumably somehow related to turn rate, yet apparently somehow unrelated to any actual aerodynamic force, is magically affecting the amount of "centrifugal force" the aircraft is generating in the slip or the skid.
If the diagrams in the answer actually include the airplane figure (I'm not much of an artist), it should be drawn yawed to the high side of the turn in the slip and yawed toward the low side of the turn in the skid.  The flight path will be drawn coming straight out of the page toward the viewer, so the little arrows suggesting that the plane is sliding down and left in the slip, and up and right in the skid, will be omitted.
One interesting question is whether the aerodynamic sideforce vectors referenced above should be considered to include the sideways thrust vector cause by yawing the thrust line sideways relative to the aircraft.  As described above, it seems they should, but interestingly, the sideways component of thrust vector has no tendency to displace the slip-skid ball, because it has no sideways component relative to the slip-skid ball, or relative to the pilot's seat for that matter.  If we include the sideways thrust vector as part of the aerodynamic sideforce vector, then we are not really using a reference frame fully aligned with the aircraft itself, but rather a reference frame aligned with the direction of the flight path through the airmass at any given instant.  It's interesting to think of other analogs-- for example, perhaps a flat-bottomed sled on an icy lake performing a turn by yawing sideways and then firing a thruster that was aimed purely in the aftwards direction in relation to the driver's seat-- that would be equivalent to a flat skidding turn that was somehow performed using only the sideforce generated by yawing the thrust line to one side, with the aerodynamic sideforce from the air hitting the side of the fuselage somehow playing only a negligible role.  One airborne analog would be a perfectly spherical airship with a fixed motor in the back, plus thrusters that could establish any desired yaw angle between the flight path and the heading.  Skidding turns in such an aircraft would not disturb the slip-skid ball.

"The net force in the diagram must be zero", yes, and one can do that by including lateral force vectors from relative wind and thrust.  Well done to continue the work here.  In the skid (under power), the lateral component consists of the horizontal  lift component (smaller) plus the horizontal thrust component plus the horizontal side force from the leeward side (it is skidding).  In the slip, the lateral component consists of the horizontal lift component (larger) minus the horizontal thrust component (now outside the turn) minus the windward side force(slipping)

Notice, the vertical lift vector and the net lateral vector are the same for all cases, matching the vertical and horizontal loads.  In a coordinated turn (theoretically), the lateral component is all horizontal lift component, the thrust is in the line of flight, and there is neither slip nor skid.  The wing is king.

@RobertDiGiovanni -- well, I know exactly how I intend to draw the diagrams-- exactly as described a month ago in this answer-- just need to sit down and do it!


text:
Is there a standard word or phrase in the English-speaking world to describe the angle between the fuselage and the flight path / relative wind?
Is there a standard word or phrase, or several alternative commonly-used words or phrases, in the English-speaking aviation world to describe the angle between the longitudinal axis of the fuselage, and the flight path/ relative wind/ undisturbed free stream airflow?
Also, is one particular greek letter commonly associated with this angle in engineering texts and papers, much as "alpha" is commonly used to describe what the English-speaking aviation world usually calls "angle-of-attack"?
Basically the angle we are asking about is conceptually much like angle-of-attack, but modified to mean the angle-of-attack of the fuselage rather than the angle-of-attack of the wing.
Note: this question is asking about an angle that we would see when looking at the fuselage and flight path in a side view, as the aircraft flies with the wings level.  This question is not asking about a yaw angle or sideslip angle.

If the fuselage is at a 0° angle to the relative wind, we would call it streamlined or maybe in the slipstream. Other than that, I can’t find any word or phrase to describe the angle itself. Interesting question, though.

I think your answer is in bold above.

Your question is confusing (at least to me). Since the wing is generally fixed to the fuselage, would not angle of attack be sufficient to describe what you are looking for? Are you asking about deck angle corrected to relative wind (the difference between deck angle and angle of attack)? Or, are you asking about a measurable angle that would be comparable to yaw (called crab)?

@JWalters the yaw version of what I am talking about is called slip, not crab.  Crab is the angle between the fuselage and the ground track which has little to do with the angle of the airflow over the aircraft.  Angle-of-attack is not sufficient to describe what am I talking about because 1) different planes have the wings fixed to the fuselage at different angles and 2) in a very few planes the angle between the wings and the fuselage is variable.

True about slip/crab. Angle of attack is usually measured on the fuselage. Why would it not be sufficient to describe what you are asking where the wing is fixed?

@JWalters, I'm not saying it's not sufficient in that case.  It is.But what is your basis for saying "angle of attack is usually measured on the fuselage"?  Sure, the probe is located there on some aircraft, but to the extent that things can or need to be defined that precisely, wouldn't the presumption be that the zero index on the gauge is set at the point where the wing is at zero degrees angle-of-attack?  (Or in some cases possibly, where the wing is at the zero-lift angle-of-attack)

(Could be grounds for another ASE question on what the zero index on a pilot's AoA gauge usually corresponds to, but this is getting off-topic from the issue of the most correct usage of terms, and from my original question.)

I state that the angle of attack is usually measured on the fuselage because that is where the vane/probe/sensor is typically placed. All §25 and §23 jets that I am aware of, including Boeing, Airbus, Bombardier, and Cessna Citation models (these are the ones that I fly) have the vane placed on the forward fuselage. See for example the issues surrounding the 737 Max. The Quest Kodiak and certain light aircraft applications including various STC mods are the exception to the above and involve measuring the AOA on the wing.

A wing will not typically have a single "zero degrees" AOA, just as a propeller will not. Wings typically have a variable angle of incidence. An AOA system may be calibrated to aircraft performance, rather than a specific aircraft angle. The manufacturer will determine what reference is appropriate. According to Boeing's Aero magazine, "most commercial jet airplanes use the fuselage centerline or longitudinal axis as the reference line."

It is just angle of attack.
Most anything can have an angle of attack. If you must be specific, you mention 'angle of attack of ...' Due to complexity of aerodynamics, most external elements of an airplane have their own local angle of attack. AoA sensors measure their angle of attack, and it is usually not even converted to 'wing' or 'fuselage'; it is dubbed 'indicated' or 'measured' and all limits are set with respect to that local AoA.
All these angles are usually designated as $\alpha$ (alpha), but with an appropriate index, which should always be explained in the nomenclature.
When we talk about airplane as a whole, usually the 'default' angle of attack is the one between the wind and the body frame (in the vertical plane). How body frame is defined depends on the aircraft designer, but normally X goes along the fuselage. Therefore, the angle of attack is exactly what you say: the angle between relative wind and the fuselage -- and not that of the wing (even though it is arguably more important).
Yet when we talk about aerodynamics, we may redefine the angle to mean 'angle of attack of the wing'. And even offset it to be with respect to zero lift. This is all fine as long as it's explicit. When we talk about just wing or airfoil, then the default angle of attack will be that of this object.

I'm not sure this is entirely correct.  See for example this link https://www.av8n.com/how/htm/aoa.html#sec-def-aoa .  I think the default understanding of "angle of attack" in the aviation world refers to the angle between flight path/ relative wind/ free stream airflow and the mean chord line of the wing, though the phrase certainly has many other uses as well.

Two comments under answers to the related question https://aviation.stackexchange.com/questions/76799/a-question-about-the-exact-meaning-of-one-british-usage-of-the-term-angle-of-in have also supported this viewpoint.

Maybe I need to ask another question asking "what is angle-of-attack"-- or maybe it already exists.

What if there is no wing? Or two wings? A body (say, a missilie) also has an angle of attack when it flies. AoA is a very generic term, and you can define it with respect to whatever body you like. The only crucial point is that it is body-to-relative-wind angle. When we consider the whole aircraft, we define AoA with respect to the aircraft, which in turn has a defined reference body axes frame.

There is a term called "deck angle", which is the angle of the cabin floor, or deck, (and normally parallel to the longitudinal axis) relative to horizontal in a given flight condition.  More or less the same thing as "pitch attitude".  These however, don't cover your question because they are relative to the horizontal.
There is another term which I think fits, called "angle of inclination", which is the vertical angle of a streamlined body relative to the freestream.  I dug up this NACA report that mentions it.  This would be the closest term to define a fuselage's angle to the freestream.

Or wing setting angle

If you’re talking about the angle between the longitudinal axis and the relative wind rotated about the vertical axis, I’m not sure there is a term per se except for coordination of flight.  The angle is not typically measured but of the angle is towards the inside of the flight path this is considered a slipping condition. When on the outside of the flight path, it’s a skidding condition.